[j-nsp] DA rejects

Doug Hanks dhanks at juniper.net
Tue Dec 20 02:28:36 EST 2011


CDP shows up as "policed discards."


On 12/18/11 1:23 PM, "Richard A Steenbergen" <ras at e-gerbil.net> wrote:

>On Thu, Dec 15, 2011 at 02:11:18PM -0500, randy.taylor at bell.ca wrote:
>> I have seen this before facing Cisco device running CDP.  Maybe you
>> have something that is running on your box that it does not
>> understand.
>
>DA Rejects are when your router receive receives a packet that is
>destined for a MAC address that "isn't it"... This is normal/expected
>behavior in small doses, since even on a switched network the unknown
>unicast flooding stage of MAC learning will result in a few packets
>being sent to ports that weren't actually the correct destinations. If
>the router was an ordinary host these would be the type of packets you
>would need to turn on "promiscuous mode" to see.
>
>This is not to be confused with L3 Incompletes, which is what you're
>probably thinking about re: CDP. This simply means a packet without a L3
>header that the router doesn't know what to do with (since the Juniper
>device doesn't speak CDP), and thus discards.
>
>-- 
>Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
>GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
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